1. Field of the Invention
The present invention relates to a burn-in board used in a burn-in test on a semiconductor product, and particularly to a burn-in board which single makes it possible to perform a burn-in test on plural kinds of semiconductor products which are equal to one another in their package and the number of pins.
2. Prior Art
In order to secure quality and reliability of a semiconductor product, a burn-in test is performed as a kind of screening tests for removing a product having a potential defect. In the burn-in test, a burn-in board is used as a board for accommodating a number of devices to be tested and the burn-in board is accommodated in a burn-in chamber and then the test is performed.
In an existing burn-in board, different kinds of devices to be tested (semiconductor products) which are equal to one another in their package and the number of pins are different in electric test conditions, and therefore, it has been necessary to change over the test circuits and so some additional boards have had to be prepared. As a method for solving such a problem, up to now, a technique is known which has been disclosed in a Japanese laid-open publication Tokkaihei No. 3-170078.
A burn-in board 100 disclosed in this publication has plural (four) IC sockets 102 on a printed wiring board 101 as shown by an external view in FIG. 8 and a circuit diagram in FIG. 9. Each of the IC sockets 102 is provided with fourteen terminals (pins) represented by numbers 1 to 14, where the terminals of numbers 1 to 6 have the corresponding signals 1 to 6 inputted to them through the respective resistors 103 and the terminals of numbers 8 to 13 have the corresponding signals 8 to 13 inputted to them through the respective resistors 103. And the terminal of number 14 is connected to a first power source (Vcc) 107 through a circuit changeover socket 104. The terminal of number 7 is connected to a second power source (the ground potential GND) 108. The circuit changeover socket 104 can put on and off selectively either one of circuit changeover units 105a and 105b. The circuit changeover socket 105a has resistors 106 and the circuit changeover socket 105b has no resistor.
This burn-in board 100 makes it possible to change a circuit (insert or remove the resistors 106 in this example) by wiring a circuit part common to plural kinds of burn-in boards as it is on the single printed wiring board 101 and collecting one-end parts of other circuit wirings than the common part at a part (circuit changeover socket 104) of the printed wiring board 101 and then putting on or off either one of the circuit changeover units 105a and 105b which have, respectively, other circuits than the common circuit.
By means of such a composition, the existing burn-in board 100 makes it possible to perform a burn-in test on plural kinds of semiconductor products which are equal to one another in the package and the number of pins.
In the existing burn-in board 100, however, since one-end parts of other circuit wirings than the common circuit part are collected at a part of the single printed wiring board, wiring length of other circuits than the common circuit on the printed wiring board 101 cannot help being longer when the wiring is drawn from an IC socket 102 more distant from the circuit changeover socket 104. And there has been a problem that a limit of expansion of a wiring pattern width due to its close pattern increases a signal noise and can have a bad influence upon devices to be tested (semiconductor products).
And some recent products have plural Vcc and GND power sources, where drawing around of the wiring comes to be complicated when collecting one-end parts of other circuit wirings than the common circuit part at a part of the printed wiring board 101. Moreover, the existing burn-in board 100 has had another problem that manners of change of circuits are greatly limited since only wirings of other circuit parts than the common circuit part can be changed.